A shooting at a local dive bar in a small Montana town killed four people, prompting a manhunt for the gunman that has stretched into the weekend and rattled residents.

The authorities identified Michael Brown, 45, as a suspect in the shooting that took place on Friday morning. It was the deadliest in Montana since 2015. Mr. Brown is an Army veteran who has struggled with mental health issues, according to his relatives, and lived close to the bar.

The violent attack rocked the town, Anaconda, a tightly knit community in Deer Lodge County. Some people said they would now lock their doors at night for the first time in years; others said they would carry firearms for protection.

Here’s what we know so far about the shooting.

What Happened in the Attack

Around 10:30 a.m. on Friday, the gunman opened fire inside the Owl Bar, killing four people before fleeing the scene and veering onto a dirt road on the outskirts of town.

Footage from a security camera shows a man leaving the bar after the shooting, according to the Division of Criminal Investigation at the Montana Department of Justice, which shared the image and identified the person as Mr. Brown. He appeared gaunt in the video, and was shirtless and wearing dark shorts.

The circumstances of the attack and what might have motivated it are unclear.

The identities of the four people who were killed have not been released, though officials said Saturday that three of the victims were patrons and one was a bartender.